An excavator is a well-known construction machine having a mobile undercarriage and an upper swing body pivotally connected to the undercarriage. Mechanical linkage is connected to the upper swing body that is movable by hydraulic cylinders to raise, lower, and curl a work tool. The mechanical linkage typically includes a boom pivotally connected at one end to the upper swing body, a stick or arm pivotally connected to a second end of the boom, and the work tool connected at a distal end of the stick. A pair of boom cylinders raises and lowers the boom, while a single stick cylinder pivots the stick relative to the boom. An additional tool cylinder is functional to curl the tool relative to the stick. Many different tools can be connected to the distal end of the stick and movable by the tool actuator, depending on the application of the excavator. These tools can include, among others, a bucket, a grapple, a shear, a hammer, a drill, a vibratory compactor, an auger, a saw, and a pulverizer.
In some applications, it may be desirable to use two or more different tools to accomplish a particular task. For example, in demolition applications, it may be helpful to use both a hammer and a bucket or a grapple and a shear. In these applications, either two machines must be placed together to complete the task (each having a different tool), or the tool of a particular machine must be periodically exchanged with another tool. Both of these solutions can be expensive, inefficient, and/or time consuming.
An alternative solution is disclosed in U.S. Patent Publication 2011/0150615 of Ishii that published on Jun. 23, 2011 (“the '615 publication”). In particular, the '615 publication discloses an excavator having two booms, two arms, and two work tools. Each linkage arrangement of boom, arm, and tool is pivotally connected to the upper structure of the excavator and controllable by a separate operator control device. Each of the two linkage arrangements has a weight and a power that is about one-half of the weight and the power of a conventional single linkage arrangement.
Although the dual linkage arrangement of the '615 publication may improve efficiency somewhat, it may still be problematic. In particular, the machine of the '615 publication may no longer be useful in applications that require the full power of the single linkage arrangement to perform a single operation. In addition, the dual linkage arrangement may suffer from instabilities during particular operations (e.g., during hoisting).
The disclosed control system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.